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    <title>Document</title>
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<body>
    <script>
        let str = 'abcdefg'
        function solution(str) {
            const arr = str.split('')
            let l = -1
            let r = arr.length 
            while(++l !== --r) {
                [arr[l], arr[r]] = [arr[r], arr[l]]
            }
            return arr.join('')
        }
        const res = solution(str)
        console.log(res)
    </script>
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